John Atkinson's 2/17/10 review measurements of the Playback Designs MPS-5 revealed less than stellar technical performance even though Michael Fremer really liked the player. I've included JA's closing measurement remarks below followed by the manufacturer's comments.

To my knowledge there was never any followup in Stereophile regarding the manufacturers reply the MPS-5 could not be adequately measured with traditional measurement techniques.

I believe Stereophile should respond to this reply in the interests of its own measurements credibility.

Len
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Early on in the testing of the Playback Designs MPS-5, worried that there was something wrong with our review sample, I took the cover off to check that all the ribbon cables were seated properly (they were) and that there was nothing obviously adrift (there wasn't). So while I was impressed by the player's standard of construction, I can't say the same about its technical performance. The relatively high level of background noise limits the MPS-5's resolution with SACD and external 24-bit data to not much better than 16-bit CD. I am puzzled, therefore, why Michael Fremer liked the sound of this player so much. Perhaps his description of its sound being "analog-like" is a clue—for reasons that are not fully understood, a signal with very-low-level random noise added is sometimes preferred, on that it is more intelligible, to the same signal without such noise.1 But I feel that the MPS-5's measured performance precludes an unreserved recommendation.—John Atkinson
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Editor: We would like to thank both Michael Fremer and John Atkinson for the time and work they put into reviewing and testing our Playback Designs MPS-5 SACD/CD player. We were very pleased that an analog lover like Michael would enjoy our digital player.

Most of the measurement results are generally to be expected from the way they were measured. What differentiates the D/A converter inside the MPS-5 from other, more conventional converters is that it uses all custom algorithms and discrete components that were not designed following classic theories and practices. A large percentage of your charts show the behavior of the MPS-5 in the frequency domain, and only two charts show the time domain, although with rigid sinewaves as test inputs. While this would be totally adequate in most cases, it isn't for the MPS-5. For instance, most of the filter algorithms inside the MPS-5 cannot be described or even defined by feeding them periodic test tones such as sinewaves and looking at frequency charts. They were designed for real music signals, and therefore "listen" to the input signal and vary accordingly, to take advantage of how our ear perceives music, which never even resembles periodic test signals. It is common knowledge that such psychoacoustic criteria hardly ever lead to ideal measurements based on steady-state test signals.

Right from the beginning, the design goals for the MPS-5 were to reach new heights in sonic performance with real music signals rather than optimum test-signal measurements. The result is that the algorithms may not perform optimally from a measurement point of view when they have to process test signals, but, as your review also confirms, they do their assigned job quite well when processing real music signals. As we are always researching new ideas, the next-generation algorithms may very well make these kind of measurements even worse—but we can assure you that it will be for the benefit of sonic performance. Isn't that what we are all after?